To add a Collada file (.dae extension file), firstly create a directory with the name of the file.
For example the Unit_Sphere.dae will be stored in the Unit_Sphere/ directory.
All the textures and files concerning the collada file will be then stored in the same directory path, and will ease its use.
To consult and use the file, you should click on the folder you're interested in.
For this case it will be the Unit_Sphere/ folder.
Once you're in the folder, you'll see the Unit_Sphere.dae file, which is our collada file we're interested in.
To consult its code, we just have to click it.
and if we want to use it, we click on the view raw button that is on the top right of the viewer.
And here it is, the raw code of the file, we just have to copy the url, and we're good to go. You should have a url like this: https://raw.githubusercontent.com/eNOVAAerospace/collada_stockage/main/Unit_Sphere/Unit_Sphere.dae